Increasing the strength of the microbubble by encapsulating it with silica

Microbubbles are very small encapsulated bubbles with a gas-filled interior, approximately 1-10 µm in diameter. Gaseous cores can be encapsulated by lipids, proteins, polymers, surfactants, or by blending lipids with proteins. With the compression of gaseous cores, deformations occur in their shape as blood passes through the capillaries and when they are exposed to ultrasound. There is shrinkage and expansion in the shell of the microbubble exposed to ultrasound. Since this causes backscattering, cavitation or bursting in the shell of the microbubble in the incoming ultrasound radiation, microbubbles are used as contrast enhancing agents in ultrasonic imaging and in applications such as drug release / gene delivery to the target. In order for microbubbles to be used in drug release, sound waves must exceed the threshold energy of the capsule. If the threshold energy of ultrasound is equal to or below the threshold energy of the capsule, contrast is provided, if the threshold energy of ultrasound is above the threshold energy of the capsule, the capsule is broken and the drug is released. According to literature studies, encapsulation has not been done with silica before, but with lipid, protein, polymer and surfactant. However, these encapsulation materials have various disadvantages such as adding rigidity to the structure, preventing contrast and decreasing stability. In this study, it was aimed to increase the microbubble stability by encapsulating the microbubble synthesized from perfluoropropane gas with high Qvalue with silica. For this purpose; The emulsion system was prepared by changing the amount of surfactant and the amount of gas used while obtaining microbubbles, and pH control was performed at each step. After obtaining the desired values by looking at the particle size and zeta potentials, TEOS was hydrolyzed and the microbubble encapsulated with silica (siloxane bond). In the characterization tests of the synthesized and encapsulated microbubbles, firstly; Dimension analysis and zeta potential values were analyzed using Zeta-Sizer Device, in the next step; TEM (Transmissive Electron Microscope) analyzes were performed to understand and interpret the surface morphology and inner parts of the microbubble.